Prime Minister Theresa May will decide if Heathrow or Gatwick will get more runways

Britain's attempts to grow trade outside the EU will be hindered without airport expansion in the South East, a study claims.

Research carried out by accountancy firm KPMG for pressure group Let Britain Fly found that London is currently not directly connected to 128 of the biggest cities in the world - those with populations over two million.

The report estimated that by 2030 there will be 77 more cities of that size, and warned that Britain will have limited capacity to connect to any of them without airport expansion.

Thirty-one of these cities will be in the emerging markets of either China or India, according to the study.

Gavin Hayes, director of Let Britain Fly, said: "Brexit makes airport expansion more important than ever because we urgently need to unlock access to new markets. Yet this cannot happen at scale without a new runway."

KPMG's global head of aviation, James Stamp, added: " Now, more than ever, UK plc needs to demonstrate both its ability and willingness to connect to trading partners and investors in the rest of the world.

"Making a positive commitment to vital UK aviation infrastructure will send a strong message that we are open for business, and would go a long way to alleviate the concern that we are missing those global connections that are so important for business, jobs, and growth."

David Cameron was expected to confirm whether expansion projects at Heathrow or Gatwick would be supported shortly after the EU referendum, but his resignation following the victory for the Leave campaign means the decision has been left for his successor as Prime Minister, Theresa May.